Chemical heater tube

ABSTRACT

A chemical heater-cartridge for producing high amounts of heat without excessive pressure rises. A sealed, thin-walled, steel tube filled with solid lithium surrounding a core of Teflon powder forms the portable heater-cartridge. The exothermic reaction of this mixture, initiated by a pyrotechnic fuze, results in a high heat output and a reduction of pressure within the cartridge. This reduction of pressure permits the use of a small-mass tube which increases the rate of heat transfer. Sulfur hexafluoride vapor (SF6) or Freon may be added under pressure to enhance the reaction rate. Alkali metals, other than lithium, and fluorocarbons, other than Teflon, may be used and are equivalent reactants.

United States Patent [191 Olson 1] 3,811,422 [451- May 21', 1974CHEMICAL HEATER TUBE [75] Inventor: Donald R. Olson, State College, Pa.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, DC.

221 Filed: on. s, 1972 211 Appl. No.: 296,361

Primary Examiner-William F. ODea Assistant Examiner-Peter D. FergusonAttorney, Agent, or Firm-R. S. Sciascia; P. Schneider 5 7] ABSTRACT Achemical heater-cartridge for producing high amounts of heat withoutexcessive pressure rises. A sealed, thin-walled, steel tube filled withsolid lithium surrounding a core of Teflon powder forms the portableheater-cartridge. The exothermic reaction of this mixture, initiated bya pyrotechnic fuze, result$ in a high heat output and a reduction ofpressure within the cartridge. This reduction of pressure permits theuse of a small-mass tube which increases the .rate of heat transfer.Sulfur hexafluoride vapor (S1 or Freon may be added under pressure toenhance the reaction rate. Alkali metals, other than lithium, andfluorocarbons, other than Teflon, may be used and are equivalentreactants. r

8 Claims, 2 Drawing Figures l. Field of the Invention nic fuze indicatedat 16. The container holds a reactant charge including an alkali metal12 surrounding a central fluorocarbon material 14. The alkali metal 12may, for example. be lithium and the fluorocarbon Tef- Thepresentinvention relates generally to heating de- 5 Ion. The chemicalreaction for such a combination vices and more particularly to aportable heating cartridge employing a mixture of solid ingredientswhich react exothermicly upon ignition. Because of their fast response.such heating cartridges make it feasible to boil water in waterinjection bottles and thus achieve the driving pressure necessary forthe injection. The heaters can also be employed to melt ice and givepreheat to a system to enhance starting capability.

2. Description of the Prior Art In the field of one-shot heating deviceschemicals which are initially contained in a closed container react togenerate heat. Such heat sources have a wide variety of uses. However,most chemical reactions employed to produce high amounts of heat alsoproduce execessive pressures within the container. The high pressuresnecessitate increases in container mass or strengthing of the containerin various other ways to prevent its destruction. Such modifications cutdown on the heat transfer capabilities of such a container and make itless efficient.

SUMMARY OF THE INVENTION A pyrotechnic fuze is employed to ignite thereaction mixture within the heater-cartridge. The alkali metal and thefluorocarbon combine to release energy in an OBJECTS OF THE INVENTION Anobject of the present invention is to produce a high heat output withina hermetically sealed container and yet not cause a pressure rise withinthat container.

A further object of the invention is to achieve a response time severalorders of magnitude higher than an electrical heater of equivalent powerrating.

Other objects, advantages, and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional view ofaheater-cartridge shown mounted in a container; and

FIG. 2 depicts a cross-sectional view taken along the line 2-2 of FIG.1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS would be: Li (solid) F. (50nd)(solid) heat 4 LiF (solid) Li C WK can better be sn ifi FIG. '2 the lithiiim fills the container 10 with the exception'ofa center core whichmay be filled with tetrafluoroethylen'e powder. As shown in FIG. 1, thetubular container 10 may be employed to heat water in a water injectionbottle to achieve the necessary driving pressure for injection.

To enhance the reaction rates, it is also desirable, but not necessary,to have a third reactant present. It has been found that sulfurhexafluoride vapor (SP or Freon gas may be added under pressure toenhance the reaction rate. Such an addition adds to the energy liberatedin the reaction.

It should be further noted that the charging pressure of the SF or Freongas is crucial. It has been found that 100 psig gives a start-up time ofA second as compared to 2-3 seconds for a 50 psig charge.

Except under unusual conditions, it is not feasible to install astoichiometric mixture of the reactants in the tube. The adiabaticreaction temperature is of the order of 6,606 E: which will melt thecontaining stmcture unless the heat is dissipated from the outside ofthe tube at an exceedingly high rate. To solve this problem, the amountof fluorocarbon used will depend upon the heat transfer capability ofthe heater tube.. The role played by the excess alkali metal in thisprocess is not passive. Due to the very high thermal conductivity ofliquid alkali metals, they serve as an excellent heat transfer mediumbetween the reactive products and the containe'rs metal wall. This factalso.

produces a heater with a very rapid response, several orders ofmagnitude higher than that in an'electrical heater of equiyalent range.

The tube is operated simply by detonatingthe fiuz e 16. A 1 inchdiameter heating cartridge, l2 inches long with Teflon added to reactwith only one third of the lithium present, produces a heat equivalentin energy to that produced by a 600 watt electrical heater operating fora period of 20 minutes.

Obviously many modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

What is claimed is: l. A portable heater tube comprising: a hermeticallysealed container; a reactant charge disposed within said container; saidreactant charge being composed of lithium, tetrafluoroethylene. and athird constituent chosen from the group consisting of sulfurhexafluoride and Freon gas; and

' means connected to said container to initiate a chemical reaction insaid reactant charge.

2. The portable heater tube of claim 1 wherein the FIG. I, whichillustrates a preferred embodiment of lithium is present in excessamounts in proportion to a the heater-cartridge. shows a tubularcontainer 10 which may be formed of stainless steel. The container [0may be hermetically sealed by a plug and pyrotechstoichiometric mixture.

3. The portable heater tube of claim 1, wherein the lithiumsubstantially fills the container with the exception of a central core,said core being substantially filled with said tetrafluoroethylene.

4. The portable heater tube of claim 1 wherein the third constituent issulfur hexafluoride at a charging pressure of at least I psig.

5. The portable heater tube of claim I wherein the third constituent isFreon gas at a charging pressure of at least 100 psig.

6. The portable heater tube of claim 5 wherein the lithium substantiallyfills the container with the exception of a central core, said corebeing substantially filled with said tetrafluoroethylene.

7. A portable heater tube comprising:

stoichiometric mixture.

2. The portable heater tube of claim 1 wherein the lithium is present inexcess amounts in proportion to a stoichiometric mixture.
 3. Theportable heater tube of claim 1, wherein the lithium substantially fillsthe container with the exception of a central core, said core beingsubstantially filled with said tetrafluoroethylene.
 4. The portableheater tube of claim 1 wherein the third constituent is sulfurhexafluoride at a charging pressure of at least 100 psig.
 5. Theportable heater tube of claim 1 wherein the third constituent is Freongas at a charging pressure of at least 100 psig.
 6. The portable heatertube of claim 5 wherein the lithium substantially fills the containerwith the exception of a central core, said core being substantiallyfilled with said tetrafluoroethylene.
 7. A portable heater tubecomprising: a hermetically sealed container; a reactant charge disposedwithin said container; said reactant charge being composed of lithiumand tetrafluoroethylene, wherein the lithium fills the container withthe exception of a central core, said core being filled with saidtetrafluoroethylene; and means connected to said container to initiate achemical reaction in said reactant charge.
 8. The portable heater tubeof claim 7 wherein the lithium is present in excess amounts inproportion to a stoichiometric mixture.